System and method for controlling power in a communication system

ABSTRACT

A method for controlling power in a communication system. A base station allocates Channel Quality Information Channels (CQICHs) to at least one mobile station, transmits CQICH information for the allocated CQICHs, and transmits power control information to the mobile stations to which the CQICHs are allocated. A mobile station receives CQICH allocation information, receives power control information, and detects the power control information allocated to the mobile station by using the CQICH allocation information.

PRIORITY

This application is a Continuation-In-Part of U.S. application Ser. No. 11/764,623, filed on Jun. 18, 2007, and a Continuation-In-Part of U.S. application Ser. No. 11/947,520, filed on Nov. 29, 2007, each of which claims priority under 35 U.S.C. § 119(a) to a Korean Patent Application filed in the Korean Intellectual Property Office on Jun. 16, 2006 and assigned Serial No. 2006-54515, the disclosures of each of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a communication system, and in particular, to a system and method for controlling power of a Mobile Station (MS) in a communication system.

2. Description of the Related Art

Extensive research on next generation communication systems are being conducted to provide users with high-speed services having various Quality of Service (QoS) levels. Meanwhile, power control schemes used in current communication systems can normally be classified as downlink (forward) power control schemes and uplink (reverse) power control schemes according to direction of power control, and can be classified as open-loop power control schemes and closed-loop power control schemes according to whether a transmitter, or a Base Station (BS), receives feedback information from a receiver, or an MS.

In downlink power control schemes, power control is performed in a BS. When the channel condition is good as a distance between the BS and an MS is short, i.e. as the MS is located in a center area of the BS, or as there is no shadowing due to obstacles, the BS allows the MS to transmit signals with minimum possible transmission power, thereby reducing interference to neighboring BSs. When channel conditions are poor, the BS increases power of transmission signals as high as needed within a possible range so the MS may normally receive transmission signals from the BS. In uplink power control schemes, power control is performed in an MS. The MS serves as a transmitter and the BS serves as a receiver, and they control power in the same manner as that in downlink power control schemes.

In open-loop power control schemes, a transmitter (BS or MS) performing power control, independently determines channel quality of a receiver (MS or BS), and performs power control depending on the channel quality, and open-loop power control scheme control power based on reversibility between downlink and uplink channels. Reversibility between downlink and uplink channels, as used herein, means that MSs having the same (or similar) location with respect to a BS will experience similar path attenuation due to similar path attenuation based on a distance from the BS, the similar antenna gain based on antenna patterns, similar shadowing effect by the topology, similar multi-path fading, etc. That is, in open-loop power control schemes, based on reversibility between downlink and uplink channels, a transmitter spontaneously estimates signal reception quality of a receiver, calculates necessary transmission power depending on the estimated signal reception quality, and then transmits signals with the calculated transmission power.

In closed-loop power control schemes, unlike in open-loop power control schemes, a transmitter controls necessary transmission power based on signal reception quality of a receiver from which it has received a feedback channel, without independently determining a channel quality. In such a closed-loop power control scheme, overhead for feedback channels occurs undesirably. However, because a transmitter can acquire information on the channel quality at the receiver, a closed-loop power control scheme can accurately control power of transmission signals, as compared to an open-loop power control scheme.

However, in a typical communication system, as a number of MSs receiving communication services from a BS increases, a closed-loop power control scheme suffers from an increase in an amount of channel quality information that the BS should receive from MSs over a feedback channel. In addition, a closed-loop power control scheme suffers from an increase in overhead of a feedback channel allocated for receiving channel quality information. Further, in a typical communication system, when a BS transmits power control information of MSs to the MSs according to channel quality information fed back from the MSs, an increase in a number of MSs increases an amount of power control information that the BS should transmit to the MSs, and the increase in the amount of power control information for the MSs causes an increase in overhead in the communication system. Therefore, a need exists for a power control scheme for reducing overhead in communication systems.

SUMMARY OF THE INVENTION

The present invention addresses at least the above-described problems and/or disadvantages and provides at least the advantages described below. Accordingly, an aspect of the present invention is to provide a system and method for controlling power in a communication system.

Another aspect of the present invention is to provide a system and method for controlling power of an MS to reduce overhead in a communication system.

Another aspect of the present invention is to provide a system and method for transmitting power control information for controlling power of an MS in a communication system.

According to an aspect of the present invention, there is provided a method for controlling power in a communication system. The power control method in a base station includes allocating Channel Quality Information Channels (CQICHs) to at least one mobile station, transmitting CQICH information for the allocated CQICHs, and transmitting power control information to the mobile station to which the CQICHs are allocated.

According to another aspect of the present invention, there is provided a method for controlling power in a communication system. The power control method in a mobile station includes receiving CQICH allocation information, receiving power control information, and detecting the power control information allocated to the mobile station by using the CQICH allocation information.

According to a further aspect of the present invention, there is provided a system for controlling power in a communication system. The power control system includes a base station for allocating CQICHs to at least one mobile station, transmitting CQICH information for the allocated CQICHs, and transmitting power control information to the mobile station to which the CQICHs are allocated; and a mobile station for receiving CQICH allocation information, receiving power control information, and detecting the power control information allocated to the mobile station by using the CQICH allocation information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram illustrating a frame structure in a communication system according to the present invention;

FIG. 2 is a schematic diagram illustrating a structure of an Uplink (UL)-MAP message field of a frame in a communication system according to the present invention;

FIG. 3 is a diagram illustrating a burst allocation information field and a power control information field in a MAP message field of a frame in a communication system according to the present invention;

FIG. 4 is a diagram illustrating a power control bit sequence for power control in a communication system according to the present invention;

FIG. 5 is a diagram illustrating allocation of Channel Quality Information Channels (CQICHs) over which a BS receives Channel Quality Information (CQI) from MSs in a communication system according to the present invention;

FIGS. 6A and 6B are diagrams illustrating a method of mapping power control information to corresponding MSs according to CQICH allocation information of the MSs in a communication system according to the present invention;

FIGS. 7A and 7B are diagrams illustrating a method of mapping power control information to corresponding MSs according to CQICH allocation information of MSs in a communication system according to the present invention;

FIG. 8 is a diagram illustrating an operation in which a BS controls power of MSs in a communication system according to the present invention;

FIG. 9 is a diagram illustrating an operation of controlling power by an MS in a communication system according to the present invention;

FIGS. 10A and 10B are schematic diagrams illustrating a power controller of a BS in a communication system according to the present invention; and

FIG. 11 is a diagram illustrating a power controller of an MS in a communication system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described in with reference to the drawings. In the following description, a description of known functions and configurations incorporated herein has been omitted for clarity and conciseness.

The present invention provides a system and method for controlling power in a communication system, for example, an Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system, which is a Broadband Wireless Access (BWA) communication system. Although the present invention will be described herein with reference to an IEEE 802.16 communication system employing Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA), by way of example, a power control system and method provided in the present invention can also be applied to other communication systems.

In addition, the present invention provides a system and method for controlling power when a communication system exchanges data between a Base Station (BS) in charge of a particular cell and a Mobile Station (MS) that is located in the cell and receives a communication service from the BS. The present invention, described below, provides a power control system and method in which a BS in charge of a particular cell transmits, to an MS receiving a communication service therefrom, power control information for controlling power of the MS in a communication system employing OFDM/OFDMA.

The present invention provides a communication system in which a BS in charge of a particular cell generates power control information of MSs according to channel information of MSs, fed back from MSs located in the BS cell, i.e. Channel Quality Information (CQI), for example, Signal-to-Interference and Noise Ratio (SINR) or Carrier-to-Interference and Noise Ratio (CINR) that the MSs have calculated and transmitted to the BS; maps the generated power control information to corresponding MSs according to allocation information of Channel Quality Information Channels (CQICHs) allocated to the MSs to receive the CQI feedback; and then transmits a message with power control information to the MSs. In other words, the BS broadcasts the message to the MSs, and upon receipt of the broadcasted message, each of the MSs detects power control information corresponding thereto, and then controls power of the associated MS according to the detected power control information.

Further, in a communication system according to the present invention, for power control for a plurality of MSs in a particular cell, a BS generates power control information of the MSs according to CQIs of the MSs, generates a power control bit sequence Power_Control_Bit_Sequence according to the generated power control information, maps the power control information to the MSs according to CQICH allocation information, i.e. maps the power control bit sequence to the MSs, and then broadcasts a message with the power control bit sequence to the MSs. Upon receipt of the message, each of the MSs detects its own power control information included in the message, and controls power associated with the MS depending on the detected power control information.

As a result, in the communication system according to the present invention, even though a number of MSs are located in a particular cell, the BS in charge of the particular cell can minimize an increase in overhead by transmitting power control information over one burst field independently for individual frames of the MSs. In addition, the BS can control power of the MSs at high speed by transmitting power control information over one burst field independently for individual frames of the MSs.

A scheme in which a BS transmits power control information of the MSs, generated depending on CQIs of the MSs, in a message can be classified as a scheme of transmitting power control information in a Fast Power Control (FPC) message in a form of a Medium Access Control (MAC) message, a scheme of transmitting power control Information Elements (IEs) in Uplink MAP (UL-MAP) IEs of a UL-MAP message, and a scheme of transmitting Fast Tracking IEs in UL-MAP IEs of the UL-MAP message. These messages including power control information of the MSs are broadcasted to all MSs located in the cell.

In addition, a scheme in which the BS transmits in the above-described messages a power control bit sequence of the power control information generated depending on CQIs received from the MSs can be classified herein into a scheme of transmitting the power control bit sequence in a power control message in the form of a MAC message, a scheme of transmitting the power control bit sequence in a MAP message, for example, Downlink MAP (DL-MAP) message or UL-MAP message, and a scheme of transmitting the power control bit sequence in DL-MAP IEs or UL-MAP IEs of a MAP message, for example, DL-MAP message or UL-MAP message. Similarly, these messages including therein the power control bit sequence are broadcasted to all MSs located in the cell.

With reference to Table 1, a description will now made of an FPC message including the power control information. Table 1 shows a format of an FPC message including power control information.

TABLE 1 Syntax Bits Notes Fast_Power_Control Message Format{  Management Message Type = 38 8 bits  Number of stations 8 bits  Power measurement frame 8 bits   for(n=0;n<Number of stations;n++){     Basic CID 16 bits      Power adjust 8 bits   } }

As shown in Table 1, the FPC message includes a ‘Management Message Type’ field indicating a type of a corresponding management message, a ‘Number of stations’ field indicating unique numbers of MSs, a ‘Power management frame’ field indicating a power management frame, a ‘Basic CID’ field indicating a basic Connection Identifier (CID) for each of MSs, and a ‘Power adjust’ field indicating power adjustment for each of the MSs. To transmit power control information of the MSs through the FPC message, the BS includes basic CIDs of the MSs in the Basic CID field of the FPC message and transmits the FPC message to the MSs.

An IEEE 802.16 communication system, a typical BWA communication system, has a frame structure, and a BS of the system efficiently allocates resources of each frame to MSs, and transmits the resource allocation information to the MSs through a MAP message. A MAP message used for transmitting the downlink resource allocation information is a DL-MAP message, and a MAP message used for transmitting uplink resource allocation information is a UL-MAP message.

When the BS transmits the downlink resource allocation information and the uplink resource allocation information through the DL-MAP message and the UL-MAP message in this manner, the MSs can decode the DL-MAP message and the UL-MAP message, transmitted from the BS, and detect therefrom power control information, and control information for the allocation locations where resources are allocated to them, and for the data that they should receive. The MSs can receive or transmit data over the downlink or the uplink by detecting the resource allocation location and control information. In addition, when transmitting data, the MSs can control transmission power using the power control information.

The MAP message is composed of different MAP IE formats according to whether it is for a downlink or an uplink, and according to a type of a data burst, i.e. according to whether the data burst is (i) a data burst to which Hybrid Automatic Repeat reQuest (HARQ) is applied (HARQ data burst), (ii) a data burst to which HARQ is not applied (Non-HARQ data burst), or (iii) control information. Therefore, the MSs should previously know a format of each MAP IE to decode the MAP IE, and each MAP IE can be distinguished using a Downlink Interval Usage Code (DIUC), for the downlink, and using an Uplink Interval Usage Code (UIUC), for the uplink.

As described above, in the BWA communication system, data transmission is performed frame by frame, and each frame is divided into a field for transmitting downlink data and a field for transmitting uplink data. The fields for transmitting data are formed in a 2-dimensional arrangement of ‘frequency domain’×‘time domain’, and each element in the 2-dimensional arrangement is a slot which is an allocation unit. That is, the frequency domain is divided in units of subchannels, each of which is a bundle of subcarriers, and the time domain is divided in units of symbols. Therefore, the slot indicates a field where a symbol is occupied by one subchannel. Each slot is allocated only to one arbitrary MS among the MSs located in one cell, and a set of slots allocated to each of MSs located in the cell is a burst. As described above, in the communication system, uplink wireless resources are allocated in such a manner that slots are shared by MSs. With reference to FIG. 1, a description will now be made of a frame structure in a communication system according to the present invention.

FIG. 1 shows a frame structure in a communication system according to the present invention. Referring to FIG. 1, the frame is shown by subchannels in the frequency domain and symbols in the time domain. The y-axis indicates subchannels which are resource units of frequency, and the x-axis indicates OFDM symbols which are resource units of time. The frame includes a preamble field 102, a DL-MAP message field 104, a UL-MAP message field 106, a downlink burst (DL Burst) field 108, and an uplink burst (UL Burst) field 110.

The preamble field 102 is used for transmitting a synchronization signal, or a preamble sequence, for acquisition of a transmission/reception period, i.e. acquisition of synchronization between a BS and MSs in a communication system. The DL-MAP message field 104 is used for transmitting a DL-MAP message, and the UL-MAP message field 106 is used for transmitting a UL-MAP message. The DL-MAP message field 104, although not shown, includes a plurality of IEs, and the IEs each include information on the corresponding downlink burst field. Similarly, the UL-MAP message field 106, although not shown, includes a plurality of IEs, and the IEs each include information on the corresponding uplink burst field and power control information of the MSs. The downlink burst field 108 is used for transmitting the corresponding downlink data burst, and the uplink burst field 110 is used for transmitting the corresponding uplink data burst. With reference to FIG. 2 and Table 2, a description will now be made of a scheme of transmitting power control IEs in UL-MAP IEs of a UL-MAP message, among the above-described schemes of transmitting power control information in a message.

FIG. 2 shows a structure of a UL-MAP message field of a frame in a communication system according to the present invention. Referring to FIG. 2, the UL-MAP message field 201 includes a UL-MAP basic information field 203 for transmitting basic information of a UL-MAP message, and a per-burst UL-MAP IE field 205 for transmitting per-burst UL-MAP IEs. The per-burst UL-MAP IE field 205 includes a CID/UIUC field 207 for transmitting CID and UIUC for per-burst allocation information and power control information of the MSs, an allocation information field 209 for transmitting burst allocation information, and an extended UIUC-dependent IE field 211 for transmitting extended UIUC-dependent IEs, and the extended UIUC-dependent IE field 211 includes a power control IE field 213 for transmitting power control IEs having power control parameters separately defined for individual MSs, for transmitting power control information of the MSs.

Table 2 shows UL-MAP IEs of a UL-MAP message, which include power control IEs.

TABLE 2 Syntax Bits UL-MAP_IE{  CID 16 bits   UIUC 4 bits  if(UIUC==15){   Extended_(—) UIUC_dependent_IE{     Power_Control_IE{       Extended_(—) UIUC=0x00 4 bits       Length 4 bits       Power_Control 8 bits     }   }  } }

As shown in Table 2, UL-MAP IEs of the UL-MAP message include CID and UIUC for per-burst allocation information and power control information of the MSs, and extended UIUC-dependent IEs, and the extended UIUC-dependent IEs include power control IEs having power control parameters separately defined for individual MSs according to power control information of the MSs. With reference to Table 3, a description will now be made of a scheme of transmitting Fast Tracking IEs in UL-MAP IEs of a UL-MAP message, among the above-described schemes of transmitting power control information in a message.

Table 3 shows UL-MAP IEs of a UL-MAP message, which include Fast Tracking IEs.

TABLE 3 Syntax Bits UL-MAP_IE{  CID 16 bits   UIUC 4 bits  if(UIUC==15){    Extended_(—) UIUC_dependent_IE{         UL-MAP_Fast_Tracking_IE{          Extended_(—) UIUC=0x07 4 bits          Length variable          Map Index 2 bits          for(i=0;i<n;1++){           Power correction 3 bits           Frequency correction 3 bits           Time correction 2 bits          }       }    }  } }

As shown in Table 3, UL-MAP IEs of the UL-MAP message, like in Table 2, include CID and UIUC for per-burst allocation information and power control information of the MSs, and extended UIUC-dependent IEs. While the extended UIUC-dependent IEs of the UL-MAP IEs of the UL-MAP message, shown in Table 2, include the power control IEs having power control parameters separately defined for individual MSs depending on the power control information of the MSs, the extended UIUC-dependent IEs of the UL-MAP IEs of the UL-MAP message, shown in Table 3, include Fast Tracking IEs of the UL-MAP message, which include power control information for all MSs located in the cell. The Fast Tracking IEs of the UL-MAP message are used as additional information in addition to the information for the MSs, previously delivered at a previous frame, and are equal to unicast allocation IEs in the UL-MAP message. In addition, the Fast Tracking IEs of the UL-MAP message can be transmitted over the power control IE field 213 of FIG. 2, over which the power control IEs shown in Table 2 are transmitted.

A description will now be made of a scheme in which a BS transmits in a foregoing message a power control bit sequence of power control information generated according to CQIs of MSs in a communication system according to the present invention. A description will then be made of a process of transmitting the message including the power control bit sequence to the MSs, and controlling power of the MSs. With reference to FIG. 3, a description will first be made of a burst allocation information field and power control information field in the MAP message field of the foregoing frame. With reference to FIG. 4, a description will be made of the power control bit sequence of the power control information that the BS has generated depending on CQIs of the MSs. Thereafter, with reference to FIG. 5, a description will be made of CQICH allocation for transmission of CQIs of the MSs, and with reference to FIGS. 6 and 7, a description will be made of a method of mapping the generated power control information to the corresponding MSs according to the CQICH allocation information.

FIG. 3 shows a burst allocation information field and a power control information field in a MAP message field of a frame in a communication system according to the present invention. Referring to FIG. 3, in the communication system, when N MSs are located in a cell, a burst field of the frame is divided into N sub-burst fields, and then allocated to the N MSs on a one-to-one basis. The allocation information of the divided burst field is transmitted to the MSs over a MAP message field of the frame, which is divided into N burst allocation information fields 310-1, 310-2, . . . , 310-N. At this point, power control information of the MSs is transmitted to the MSs over one power control information field 320 divided from the MAP message field. That is, in a communication system according to the present invention, power control information of all MSs located in a particular cell is transmitted to the MSs, i.e. broadcasted to the MSs, over the one power control information field 320 allocated in the MAP message field of the frame. Accordingly, in a communication system according to the present invention, even though a number of MSs located in a particular cell increases, the system can minimize an increase in overhead as a BS in charge of the cell transmits per-frame power control information of the MSs over the one power control information field 320 allocated in the MAP message field of the frame. In addition, a communication system according to the present invention can rapidly control power of the MSs as the BS transmits per-frame power control information of the MSs over the one power control information field 320 allocated in the MAP message field of the frame.

FIG. 4 shows a power control bit sequence for power control in a communication system according to the present invention. Referring to FIG. 4, in the communication system, a BS generates power control information of MSs according to CQIs received from N MSs located in the cell of the BS, and generates a power control bit sequence of the MSs, i.e. N power control bits 410-1, 410-2, . . . , 410-N for the MSs, according to the generated power control information. The power control bits 410-1, 410-2, . . . , 410-N of the MSs are each composed of m bits.

More specifically, for m=1, indicating that the power control bits 410-1, 410-2, . . . , 410-N of the MSs are each composed of 1 bit, when the power control bits 410-1, 410-2, . . . , 410-N of the MSs are set to ‘0’, the MSs are ordered to keep the current power level, and when the power control bits 410-1, 410-2, . . . , 410-N of the MSs are set to ‘1’, the MSs are ordered to increase or decrease the current power level by a threshold. For m=2, indicating that the power control bits 410-1, 410-2, . . . , 410-N of the MSs are each composed of 2 bits, when the power control bits 410-1, 410-2, . . . , 410-N of the MSs are set to ‘00’, the MSs are ordered to keep the current power level; when the power control bits 410-1, 410-2, . . . , 410-N of the MSs are set to ‘01’, the MSs are ordered to increase the current power level by a threshold; and when the power control bits 410-1, 410-2, . . . , 410-N of the MSs are set to ‘11’, the MSs are ordered to decrease the current power level by a threshold. For m=n, indicating that the power control bits 410-1, 410-2, . . . , 410-N of the MSs are each composed of n bits, power of the MSs is changed in a type of a signed integer. For example, for n=5, when the power control bits 410-1, 410-2, . . . , 410-N of the MSs are set to ‘00100’, the MSs are ordered to increase the current power level by 4 times a threshold, and when the power control bits 410-1, 410-2, . . . , 410-N of the MSs are set to ‘11100’, the MSs are ordered to decrease the current power level by 4 times a threshold. Current power level, as used herein, refers to a transmission power level used when the MSs transmit their CQIs to the BS over CQICHs, and the ‘threshold’ refers to a particular value by the user or the system according to communication system and communication environment.

FIG. 5 shows allocation of CQICHs over which a BS receives CQIs from MSs in a communication system according to the present invention. Referring to FIG. 5, the BS of the communication system includes, in an (n-k)^(th) frame 501, a preamble field 551, a DL-MAP message field 553, a UL-MAP message field 555, a downlink burst field 557, and an uplink burst field 559, as described in FIG. 1. The BS transmits to MSs a UL-MAP message which is transmitted over the UL-MAP message field 555 of the (n-k)^(th) frame 501, and allocates it to a downlink burst field 571 of an n^(th) frame 503 to provide the MSs with information on a CQI field 573 indicating CQIs to be transmitted by the MSs, and information on a CQICH field 577 allocated such that the MSs may transmit CQIs over it according to information transmitted over the CQI field 573. That is, the BS broadcasts to the MSs the UL-MAP message transmitted over the UL-MAP message field 555 of the (n-k)^(th) frame 501, so the MSs can acquire information on the CQICH field 577 allocated to the MSs themselves in an uplink burst field 575 of the n^(th) frame 503 and information on CQIs transmitted over the allocated CQICH field 577. With reference to FIGS. 6A and 7A, a detailed description will now be made of CQICH allocation to the MSs, and with reference to FIGS. 6B and 7B, a description will be made of mapping of power control information to the corresponding MSs according to the CQICH allocation of FIGS. 6A and 7A.

FIGS. 6A and 6B show a method of mapping power control information to corresponding MSs according to CQICH allocation information of the MSs in a communication system according to the present invention. Referring to FIGS. 6A and 6B, in the communication system, when there are N MSs located in a cell, a CQICH field in an uplink burst field of a frame is divided into N sub-CQICH fields 610-1, 610-2, 610-3, . . . , 610-(N−1), 610-N, and then allocated to the N MSs on a one-to-one basis. The allocation information of the divided CQICH field is broadcasted to the N MSs over a MAP message field, i.e. the UL-MAP message field, of the frame as described above. The sub-CQICH fields 610-1, 610-2, 610-3, . . . , 610-(N−1), 610-N are allocated to the MSs at every frame so the MSs may transmit CQIs to the BS over them. As described above, based on the MAP message, the MSs each recognize CQICHs allocated to them by the BS, in other words, recognize indexes CQI #1, CQI #2, CQI #3, . . . , #CQI #(N−1) and CQI #N of CQICHs, for example, unique numbers and allocation orders of CQICHs allocated to them at every frame by the BS.

For convenience, it will be assumed herein that the BS allocates a sub-CQICH field 610-1 with a CQICH index=CQI #1 to a first MS among the N MSs, allocates a sub-CQICH field 610-2 with a CQICH index=CQI #2 to a third MS, allocates a sub-CQICH field 610-3 with a CQICH index=CQI #3 to a second MS, allocates a sub-CQICH field 610-(N−1) with a CQICH index=CQI #(N−1) to an N^(th) MS, and allocates a sub-CQICH field 610-N with a CQICH index=CQI #N to an (N−1)^(th) MS. Then the MSs, because they already know indexes of CQICHs allocated to them from the MAP message as described above, transmit their CQIs to the BS over sub-CQICH fields corresponding to the recognized CQICH indexes.

Upon receipt of CQIs from the MSs over CQICHs, the BS generates power control information of the MSs and generates a power control bit sequence according to the generated power control information as described above, and then maps the generated power control information for the MSs to the corresponding MSs according to the CQICH allocation information of the MSs. That is, when all CQICH channels are allocated to all of N MSs, as shown in FIG. 6A, the BS maps the power control information for the MSs to the corresponding MSs in a message, for example, a MAP message field, i.e. DL-MAP message field or UL-MAP message field, of a frame, according to the CQICH allocation information of the MSs, as shown in FIG. 6B.

That is, as the BS generates power control information according to the CQIs after allocating CQICHs to all of N MS and receiving the CQIs over the allocated CQICHs as described above, one power control information field allocated for transmitting power control information for the MSs is divided into N sub-fields 660-1, 660-2, 660-3, . . . , 660-(N−1) and 660-N, where N is the number of MSs, as described in FIG. 3, and then mapped to the N MSs, i.e. allocated to the N MSs on a one-to-one basis. The N sub-fields 660-1, 660-2, 660-3, . . . , 660-(N−1) and 660-N are mapped according to the CQICH allocation information of the MSs, for example, indexes of CQICHs allocated to the MSs.

Under the foregoing assumption given for convenience, a first sub-field 660-1 among the N sub-fields 660-1, 660-2, 660-3, . . . , 660-(N−1) and 660-N is mapped, or allocated, to the first MS to which the sub-CQICH field 610-1 with a CQICH index=CQI #1 is allocated; a second sub-field 660-2 is mapped, or allocated, to the third MS to which the sub-CQICH field 610-2 with a CQICH index=CQI #2 is allocated; a third sub-field 660-3 is mapped, or allocated, to the second MS to which the sub-CQICH field 610-3 with a CQICH index=CQI #3 is allocated; an (N−1)^(th) sub-field 660-(N−1) is mapped, or allocated, to the N^(th) MS to which the sub-CQICH field 610-(N−1) with a CQICH index=CQI #(N−1) is allocated; and an N^(th) sub-field 660-N is mapped, or allocated, to the (N−1)^(th) MS to which the sub-CQICH field 610-N with a CQICH index=CQI #N is allocated. The power control information is transmitted to the MSs, i.e. broadcasted to N MSs located in the cell, over the sub-fields 660-1, 660-2, 660-3, . . . , 660-(N−1) and 660-N, which are allocated to the MSs according to the CQICH allocation information of the MSs. Then, the MSs each recognize, from the CQICH allocation information included in the MAP message field, a sub-field over which power control information associated with each MS is transmitted, the sub-field being allocated in the one power control information field, detect power control information transmitted over the sub-field, and control power for the associated MS depending on the detected power control information.

FIGS. 7A and 7B show a method of mapping power control information to corresponding MSs according to CQICH allocation information of MSs in a communication system according to the present invention. A description of FIGS. 7A and 7B is given herein for a case where no CQICH is allocated to the third MS and the (N−1)^(th) MS in FIGS. 6A and 6B, and thus, the third MS and the (N−1)^(th) MS do not transmit their CQIs to the BS.

Referring to FIGS. 7A and 7B, in a communication system, when there are N MSs located in a cell, a CQICH field in an uplink burst field of a frame is divided into N sub-CQICH fields 710-1, 710-2, 710-3, . . . , 710-(N−1) and 710-N, and then allocated to the N MSs on a one-to-one basis. The allocation information of the divided CQICH field is broadcast to the N MSs over a MAP message field, i.e. UL-MAP message field, of the frame, as described above. In addition, the sub-CQICH fields 710-1, 710-2, 710-3, . . . , 710-(N−1) and 710-N are allocated to the MSs at every frame so that the MSs may transmit CQIs to the BS. As described above, based on the MAP message, the MSs each recognize CQICHs allocated to them by the BS, in other words, recognize indexes CQI #1, CQI #2, CQI #3, . . . , #CQI #(N−1) and CQI #N of CQICHs, for example, unique numbers and allocation orders of CQICHs allocated to them at every frame by the BS.

Under the foregoing assumption that the BS allocates no CQICH to the third MS and the (N−1)^(th) MS among the N MSs, because the BS allocates a sub-CQICH field 710-1 with a CQICH index=CQI #1 to a first MS among the N MSs and allocates no CQICH to the third MS, a sub-CQICH field 710-2 with a CQICH index=CQI #2 is not allocated, and because the BS allocates a sub-CQICH field 710-3 with a CQICH index=CQI #3 to a second MS, allocates a sub-CQICH field 710-(N−1) with a CQICH index=CQI #(N−1) to an N^(th) MS, and allocates no CQICH to an (N−1)^(th) MS, a sub-CQICH field 710-N with a CQICH index=CQI #N is not allocated. Then, the MSs, because they already know indexes of CQICHs allocated to them from the MAP message as described above, transmit their CQIs to the BS over sub-CQICH fields corresponding to the recognized CQICH indexes. That is, while the BS in FIG. 6A allocates CQICHs so all of N MSs may transmit their CQIs to the BS, i.e. allocates the N sub-fields 660-1, 660-2, 660-3, . . . , 660-(N−1) and 660-N to all of N MSs, respectively, the BS in FIG. 7A allocates no CQICH to the third MS and the (N−1)^(th) MS among the N MSs so they do not transmit their CQIs to the BS, and thus, the sub-CQICH fields 710-2 and 710-N with CQICH index=CQI #2 and CQI #N are not allocated to the MSs.

Upon receipt of CQIs over CQICHs from the MSs except for the third MS and the (N−1)^(th) MS among the N MSs, the BS generates power control information of the MSs and generates a power control bit sequence according to the generated power control information as described above, and then maps the generated power control information of the MSs to the corresponding MSs according to the CQICH allocation information of the MSs. That is, when CQICH channels are allocated to the remaining MSs except for the third MS and the (N−1)^(th) MS among the N MSs, as shown in FIG. 7A, the BS maps the power control information for the MSs to the corresponding MSs in a message, for example, a MAP message field, i.e. DL-MAP message field or UL-MAP message field, of a frame, according to the CQICH allocation information of the MSs, as shown in FIG. 7B.

That is, as the BS generates power control information according to the CQIs after allocating CQICHs to the remaining MSs except for the third MS and the (N−1)^(th) MS among the N MS and receiving the CQIs over the allocated CQICHs as described above, one power control information field allocated for transmitting power control information for the MSs is divided into N sub-fields 760-1, 760-2, 760-3, . . . , 760-(N−1) and 760-N, where N is the number of MSs, as described in FIG. 3, and then mapped, i.e. allocated, to the remaining MSs except for the third MS and the (N−1)^(th) MS among the N MSs, respectively. The N sub-fields 760-1, 760-2, 760-3, . . . , 760-(N−1) and 760-N are mapped according to the CQICH allocation information of the MSs, for example, indexes of CQICHs allocated to the MSs.

Under the foregoing assumption given for convenience, a first sub-field 760-1 among the N sub-fields 760-1, 760-2, 760-3, . . . , 760-(N−1) and 760-N is mapped, or allocated, to the first MS to which the sub-CQICH field 710-1 with a CQICH index=CQI #1 is allocated; a second sub-field 760-2 is not mapped, or not allocated, to any MS as the sub-CQICH field 710-2 with a CQICH index=CQI #2 is not allocated; a third sub-field 760-3 is mapped, or allocated, to the second MS to which the sub-CQICH field 710-3 with a CQICH index=CQI #3 is allocated; an (N−1)^(th) sub-field 760-(N−1) is mapped, or allocated, to the N^(th) MS to which the sub-CQICH field 710-(N−1) with a CQICH index=CQI #(N−1) is allocated; and an N^(th) sub-field 760-N is not mapped, or not allocated, to any MS as the sub-CQICH field 710-N with a CQICH index=CQI #N is not allocated. The power control information is transmitted to the MSs, i.e. broadcasted to N MSs located in the cell, over the sub-fields 760-1, 760-3, . . . , 760-(N−1), which are allocated to the MSs according to the CQICH allocation information of the MSs. Then, the MSs each recognize, from the CQICH allocation information included in the MAP message field, a sub-field over which its power control information is transmitted, the sub-field being allocated in the one power control information field, detect power control information transmitted over the sub-field, and control power associated with each MS depending on the detected power control information. Of the second sub-field 760-2 and the N^(th) sub-field 760-N not allocated to the MSs, the N^(th) sub-field 760-N can be allocated for transmission of data other than transmission of power control information, thereby contributing to a reduction in length of a power control burst and to efficient use of resources. A description will now be made of a scheme in which a BS transmits in a message the power control bit sequence of the power control information generated according to CQIs received from MSs in the communication system according to the present invention.

Table 4 shows a format of a MAP message when the BS generates a power control bit sequence of power control information generated according to CQIs received from MSs and transmits the power control bit sequence in the MAP message, for example, DL-MAP message or UL-MAP message, in the communication system according to the present invention.

TABLE 4 Syntax Bits MAP Message{  ...  Power_Control_Broadcasting{     Length x-bits     Power_Control_Bit_Sequence variable   } }

As shown in Table 4, the MAP message includes a Power_Control_Broadcasting field, and the Power_Control_Broadcasting field includes a ‘Length’ field indicating a length of the Power_Control_Broadcasting field, and a Power_Control_Bit_Sequence field indicating a power control bit sequence generated according to power control information of the MSs. The power control bit sequence has been described with reference to FIG. 4, and length information of the power control bit sequence is transmitted to the MSs over a Downlink Channel Descriptor (DCD) or an Uplink Channel Descriptor (UCD). The DCD and the UCD are messages periodically transmitted with defined physical channel characteristics of the downlink and the uplink, respectively, and these are not directly related to the present invention, so associated descriptions are omitted. The BS broadcasts in the MAP message to the MSs a power control bit sequence with power control information generated according to CQIs received over CQICHs from the MSs.

Table 5 shows MAP IEs when the BS transmits in DL-MAP IEs or UL-MAP IEs of a MAP message, for example, DL-MAP message or UL-MAP message, a power control bit sequence of power control information generated according to CQIs received from the MSs in the communication system according to the present invention.

TABLE 5 Syntax Bits DL(or UL)-MAP_IE{  CID=FFFF(Broadcasting CID) 16 bits   DIUC(or UIUC) 4 bits  Extended-DIUC(or(UIUC)_dependent_IE{    Power_Control_Broadcast_IE{      Extended_(—) DIUC(or UIUC) 4 bits      Length x-bits      Power_Control_Bit_Sequence variable    }   } }

As shown in Table 5, the DL-MAP IEs or UL-MAP IEs of the DL-MAP message or UL-MAP message include CID and UIUC or DIUC for per-burst allocation information and power control information of the MSs, and extended UIUC-dependent IEs or extended DIUC-dependent IEs. The extended UIUC-dependent IEs or extended DIUC-dependent IEs include the power control bit sequence. With reference to Table 6, a description will now be made of a method in which the BS transmits, in a power control message in a type of a MAC message other than the MAP message, the power control bit sequence of power control information generated according to CQIs received from the MSs in the communication system according to the present invention.

Table 6 shows a format of a power control message when a BS transmits in a power control message a power control bit sequence of power control information generated according to CQIs received from MSs in a communication system according to the present invention.

TABLE 6 Syntax Bits Power_Control_Message{  Management Message Type 8 bits   Length x-bits  Power_control_Bit_Sequence variable }

As shown in Table 6, the power control message includes a ‘Management Message Type’ field indicating a type of the corresponding management message, a ‘Length’ field indicting a length of the MAC message, and a Power_Control_Bit_Sequence field indicating a power control bit sequence generated according to power control information of the MSs. With reference to FIG. 8, a description will now be made of an operation in which a BS controls power of MSs in a communication system according to the present invention.

FIG. 8 shows an operation in which a BS controls power of MSs in a communication system according to the present invention. Referring to FIG. 8, in step 801, the BS receives CQIs of MSs over CQICHs previously allocated to receive CQIs from the MSs located in the cell of the BS, and generates power control information of the MSs according to the received CQIs. Herein, in order to generate power control information, for example, the CQICH is used. However, the power control information can be generated using, for example, uplink traffic bursts of the MS or uplink traffic bursts of the MS corresponding to the CQICH as well as the CQICH. Thereafter, in step 803, the BS generates a power control bit sequence according to the generated power control information as described with reference to FIG. 4. An operation of generating the power control bit sequence has been described in FIG. 4.

Next, in step 805, the BS allocates CQICHs to the MSs so the MSs may transmit their CQI information as described above, and maps the power control information to the corresponding MSs according to the CQICH allocation information. That is, the BS divides one power control information field previously allocated for transmission of the power control information generated in step 801, according to the number of the MSs, and then allocates the divided power control information fields to the MSs according to the CQICH allocation information, thereby mapping the power control information to the corresponding MSs. An operation of mapping the power control information to the MSs according to the CQICH allocation information has been described with reference to FIGS. 6 and 7.

In step 807, the BS includes the power control bit sequence generated in step 803 in a message, and then transmits, or broadcasts, the message including the power control bit sequence to the MSs located in the cell. The message including the power control bit sequence of the generated power control information is a power control message in a type of a MAC message, or a MAP message, and is broadcast to the MSs. With reference to FIG. 9, a description will now be made of an operation of controlling power by an MS in a communication system according to the present invention.

FIG. 9 shows an operation of controlling power by an MS in a communication system according to the present invention. Referring to FIG. 9, in step 901, the MS transmits a CQI of the MS to a BS of the MS over a CQICH allocated by the BS, and upon receipt of a message from the BS, detects a power control bit sequence included in the message. Based on information included in the message received from the BS, the MS recognizes a field where the power control bit sequence is transmitted. An operation of generating, by the BS, power control information of the MS according to the CQI and transmitting the message including the power control information has been previously described. In addition, an operation of recognizing, by the MS, the field where the power control bit sequence is transmitted, based on the information included in the message received from the BS, is equal to the operation of recognizing one power control information field based on the MAP message, so a description thereof will be omitted.

Thereafter, in step 903, the MS detects power control information corresponding thereto from the power control information transmitted over the power control information field according to the CQICH allocation information included in the message. That is, because the BS maps the power control information to the corresponding MSs according to the CQICH allocation information before transmission as described above, the MS detects power control information of the MS according to the mapping. An operation of detecting the power control information by the MS has been described above. Next, in step 905, the MS controls transmission power of the MS, i.e. power of a transmission signal to the BS, according to the power control information detected in step 903.

FIGS. 10A and 10B show a power controller of a BS in a communication system according to the present invention. The power controller shown in FIG. 10A is for a case where a BS transmits a power control bit sequence in a MAP message, and the power controller shown in FIG. 10B is for a case where a BS transmits a power control bit sequence in a MAC message, i.e. power control message.

Referring to FIG. 10A, the power controller of the BS includes a CQICH allocator 1001 for allocating CQICHs to receive CQIs from MSs located in the cell of the BS, a power control information generator 1003 for receiving CQIs of the MSs over the CQICHs allocated by the CQICH allocator 1001 and generating power control information of the MSs according to the received CQIs, a power control bit sequence generator 1005 for generating a power control bit sequence according to the power control information generated by the power control information generator 1003 as described with reference to FIG. 4, and a MAP message generator 1007 for generating a MAP message including the CQICH allocation information of MSs, allocated by the CQICH allocator 1001, and the power control bit sequence generated by the power control bit sequence generator 1005, and then broadcasting the generated MAP message to the MSs. The power control bit sequence generator 1005 maps the power control information of the MSs, received from the power control information generator 1003, to the corresponding MSs according to the CQICH allocation information of the MSs, allocated by the CQICH allocator 1001, and then transmits the generated power control bit sequence to the MAP message generator 1007. This power control operation of the BS has been described above.

Referring to FIG. 10B, the power controller of the BS of FIG. 10B is similar to the power controller of the BS of FIG. 10A, except that the power controller of FIG. 10A includes a MAP message generator 1007 for transmitting the power control bit sequence in a MAP message, whereas the power controller of FIG. 10B includes a MAC message generator 1057 for transmitting a power control bit sequence in a MAC message.

More specifically, the power controller of the BS of FIG. 10B includes a CQICH allocator 1051 for allocating CQICHs to receive CQIs from MSs located in the cell of the BS, a power control information generator 1053 for receiving CQIs of the MSs over the CQICHs allocated by the CQICH allocator 1051 and generating power control information of the MSs according to the received CQIs, a power control bit sequence generator 1055 for generating a power control bit sequence according to the power control information generated by the power control information generator 1053 as described with reference to FIG. 4, and a MAC message generator 1057 for generating a MAC message including the CQICH allocation information of the MSs, allocated by the CQICH allocator 1051, and the power control bit sequence generated by the power control bit sequence generator 1055, and then broadcasting the generated MAC message to the MSs. The power control bit sequence generator 1055 maps the power control information of the MSs, received from the power control information generator 1053, to the corresponding MSs according to the CQICH allocation information of the MSs, allocated by the CQICH allocator 1051, and then transmits the generated power control bit sequence to the MAC message generator 1057. This power control operation of the BS has been described above.

FIG. 11 shows a power controller of an MS in a communication system according to the present invention. Referring to FIG. 11, the power controller of the MS includes a CQICH allocation decider 1101 for, upon receipt of a message from a BS, determining whether a CQICH of the MS is allocated depending on CQICH allocation information included in the message, and detecting CQICH allocation information from the message when it is determined that the CQICH of the MS is allocated, a power control bit sequence detector 1103 for detecting a power control bit sequence included in the message, a power control information detector 1105 for detecting power control information corresponding to the MS itself from the power control bit sequence detected by the power control bit sequence detector 1103 according to the CQICH allocation information detected by the CQICH allocation decider 1101, and a power controller 1107 for controlling transmission power to the BS according to the power control information detected by the power control information detector 1105. The power control bit sequence detector 1103 recognizes a field where the power control bit sequence is transmitted, depending on the information included in the message received from the BS, and because the BS maps the power control information to the corresponding MSs according to the CQICH allocation information before transmission, the power control information detector 1105 detects power control information according to the mapping. This power control operation of the MS has been described before. For power control, the base station transmits power control information, for example, a power control information element.

For the above, Table 7 shows a power control information element provided in the present invention.

TABLE 7 Syntax Size Notes Power control IE ( ) { Extended UIUC 4 bits Fast power control = 0x00 Frame offset 2 bits The offset between corresponding CQICH allocation frame and current frame. Start value shall be 1. No. PC command bits 2 bits 00: 1bit, ‘0’ -> −0.5 dB, ‘1’-> +0.5 dB (b) 01: 2bits, ‘00’ -> −0.5 dB, ‘01’ -> 0 dB, ‘10’ -> +0.5 dB, ‘11’-> +1.0 dB 10: 3bits, ‘000’-> −1.5 dB, . . . , ‘111’-> 2.0 dB, Step size = 0.5 dB 11: 4bits, ‘0000’-> −3.5 dB, . . . , ‘1111’-> 4.0 dB, Step size = 0.5 dB No. PC commands (p) 4 bits Number of the power control commands in this bitmap, represented by 4 × (p + 1). Power control Bitmap variable Power control bitmap (4 * (p + 1) * (b + 1)) bits }

As shown in Table 7, the power control information element includes an Extended Uplink Information Usage Code (Extended UIUC) indicating fast power control, a frame offset indicating the offset between the frame to which Channel Quality Information Channel (CQICH) of the MS according to each power control bit is allocated and the current frame, No. PC command bits indicating the number (b) of the bits of the Power Control command (PC command), No. PC commands indicating the number of the power control command included in a power control command bitmap, and the power control bitmap including the power control information.

The power control bitmap includes the power control information. The power control bitmap can be transmitted in the form of a bitmap, but can be transmitted in the form of a sequence as described above.

The extended UIUC indicates that, for example, a map message is a message for fast power control.

The frame offset indicates the offset between the frame including the CQICH allocation information that is allocated from the BS to the MS to receive channel quality information (CQI) and the frame including the power control information element. It is assumed that the frame offset is N. If the frame in which the CQICH allocation information is included is N^(th) frame, the frame in which the current power control information is included is (N+n)^(th) frame. When the frame offset bit is “00”, the frame offset is 1 (n=1), when the frame offset bit is “01”, the frame offset is 2 (n=2), when the frame offset bit is “10”, the frame offset is 3 (n=3), and when the frame offset bit is “11”, the frame offset is 4 (n=4). In addition, the frame offset can have a particular fixed value. And, the frame offset is not included in the power control information element and can be stored in the base station and the mobile stations in advance.

The No. PC command bits indicate the number of bits of each power control command, and for example, 2 bits are shown. For example, for No. PC command bits b=‘00’(b=‘00’), indicating that the power control command is set to 1 bit. Wherein, when the power control command is set to “0”, it means 0.5 dB power attenuation (−0.5 dB) and when the power control command is set to “1”, it means 0.5 dB power increase (+0.5 dB). For example, if 1 bit power control command is used, the power control command is selected in a power control command set including two power control commands, ‘0’ and ‘1’.

For the power control bits b=‘01’, indicating that the power control command is set to 2 bit. Wherein, when the power control command is set to ‘00’, it means 0.5 dB power attenuation (−0.5 dB), when the power control command is set to ‘01’, it means 0 dB power maintenance (0 dB), when the power control command is set to ‘10’, it means 0.5 dB power increase (+0.5 dB), and when the power control command is set to ‘11’, it means 1.0 dB power increase (+1.0 dB).

For the power control bits b=‘10’, indicating that the power control command is 3 bit. Wherein, when the power control command is set to ‘000’, it means 1.5 dB power attenuation (−1.5 dB), when the power control command is set to ‘111’, it means 2.0 dB power increase (+2.0 dB), and the power step size of the bitmap between ‘000’ and ‘111’ is set to 0.5 dB. That is, the power control command has the value between ‘000’ and ‘111’, and respectively indicating power change −1.5 dB (000), −1.0 dB (001), −0.5 dB (010), 0 dB (011), +0.5 dB (100), +1.0 dB (101), +1.5 dB (110), and +2.0 dB (111).

For the power control bits b=‘11’, indicating that the power control command is 4 bit. Wherein, when the power control command is set to ‘0000’, it means 3.5 dB power attenuation (−3.5 dB), when the power control command is set to ‘1111’, it means 4.0 dB power increase (+4.0 dB), and the difference of the power step size between ‘0000’ and ‘1111’ is set to 0.5 dB. That is, the power control command has the value between ‘0000’ and ‘1111’, and respectively indicating power change −3.5 dB (0000), −3.0 dB (0001), −2.5 dB (0010), −2.0 dB (0011), −1.5 dB (0100), −1.0 dB (0101), −0.5 dB (0110), 0 db (0111), +0.5 dB (1000), +1.0 dB (1001), +1.5 dB (1010), +2.0 dB (1011), +2.5 dB (1100), +3.0 dB (1101), +3.5 dB (1110), and +4.0 dB (1111).

The No. PC commands indicate the number of the power control commends included in a power control command bitmap. For example, each of the number of the power control command included in the power control bitmap represents 4*(p+1). For example, if the number of the power control command is ‘20’, the p value has a binary number ‘0100(4)’ value.

The power control bitmap includes the power control command and has the size of 4*(p+1)(b+1) bit. Each power control command has the size between 1 bit to 4 bit according to the value of b. And, the power control command is mapped with the power control information according to each bit value. Accordingly, the MS performs the power control using the power control information. For example, when the power control command is ‘1100’, the MS increases the current power by 2.5 dB.

As shown in Table 7, the power control information element including at least one of the frame offset, No. PC command bits, No. PC commands, and the power control bitmap and is transmitted.

As the power command values corresponding to the frame offset, the No. PC command bits, No. PC commands, the power control bit, and the power control bit value respectively are shown as examples, the power command values are not limited by the values shown in Table 7, and the power command values can be changed, for example, based on the system situation, the user setup, etc.

The power control information element can be included, for example, in a MAP message (UL-MAP or DL-MAP) and can be transmitted.

Further, FIG. 8 shows another example of a power control information element provided in the present invention.

TABLE 8 Syntax Size Notes Power control IE ( ) { Extended UIUC 4 bits Fast power control = 0x00 Frame offset 2 bits The offset between corresponding CQICH allocation frame and current frame. Start value shall be 1. No. PC command bits 2 bits 00: not consider (b) 01: 2bits, ‘00’ -> −0.5 dB, ‘01’ -> 0 dB, ‘10’ -> +0.5 dB, ‘11’-> +1.0 dB 10: 3bits, ‘000’-> −1.5 dB, . . . , ‘111’-> 2.0 dB, Step size = 0.5 dB 11: 4bits, ‘0000’-> −3.5 dB, . . . , ‘1111’-> 4.0 dB, Step size = 0.5 dB No. PC commands (p) 4 bits Number of the power control commands in this bitmap, represented by I = 4 × (p + 1). IF (b!=00) { Power control bitmap 4 × (p + 1) The i-th bit indicates whether the i-th power Indicator bits control command in Power Control bitmap is present (‘1’) or not (‘0’), I equals to the number of ‘1’s in the Power control bitmap Indicator } Power control Bitmap variable Power control bitmap (4 * I * (B + 1)) bits }

As shown in Table 8, the power control information element includes an Extended Uplink Information Usage Code (Extended UIUC) indicating fast power control, a frame offset indicating the offset between the frame to which Channel Quality Information Channel (CQICH) of the MS according to each power control bit is allocated and the current frame, No. PC command bits indicating the number (b) of the bits of the Power Control command (PC command), No. PC commands indicating the number of the power control command included in a power control command bitmap, power control bitmap indicator and the power control bitmap including the power control information.

The power control bitmap includes the power control information. The power control bitmap can be transmitted in the form of a bitmap, but can be transmitted in the form of a sequence.

The extended UIUC indicates that, for example, a map message is a message for fast power control.

The frame offset indicates location information of a specific frame including the CQICH allocation information according to information indicating power control bitmap indicator. Information indicating power control bitmap indicator corresponds to a connection identifier (ID) (or mobile station identification information) included to the CQICH allocation information included to the specific frame and the CQICH allocation sequence.

Accordingly, the frame offset indicates the frame including the CQICH allocation information and the offset between current frames including power control information element. It is assumed that the frame offset is N. Herein, if the frame including the CQICH allocation information according to information of power control bitmap indicator is N^(th) frame, the frame including power control information is (n+N)^(th) frame. When the frame offset bit is “00”, the frame offset is 1 (n=1), when the frame offset bit is “01”, the frame offset is 2 (n=2), when the frame offset bit is “10”, the frame offset is 3 (n=3), and when the frame offset bit is “11”, the frame offset is 4 (n=4).

As with the previous example, the offset is represented by adding the number of a particular frame to a value of the offset bit. For example, if the number of the particular frame is “1”, the frame offset can be the same as the frame offset of the embodiment described above. Further, for the other example, if the number of the particular frame is “2” and the offset bit is “01”, the value the frame offset can be “3”. For the other example, the frame offset can have a particular fixed value. And, the frame offset is not included in the power control information element and can be stored in the base station and the mobile stations in advance

The No. PC command bits indicate the number of bits of each power control command, and for example, 2 bit is described. For example, if No. PC command bits b is ‘00’ (b=‘00’), the power control command as described in Table 7 indicates 1 bit. Wherein, when the power control command is set to “0”, it means 0.5 dB power attenuation (−0.5 dB) and when the power control command is set to “1”, it means 0.5 dB power increase (+0.5 dB). For example, if 1 bit power control command is used, the power control command is selected in a power control command set including two power control commands, ‘0’ and ‘1’.

However, Table 8 is directed to the embodiment according to the case that b is not “00”, that is, the bit value of b is not “0” (‘1(01)’, ‘2(10)’ and ‘3(11)’). Therefore, if the bit value of b is not “0”, the power control bitmap indicator is used for indicating whether the power control command of each mobile station exists.

If the power control bits b is ‘01’, the power control command is set to 2 bit. Wherein, when the power control command is set to “00”, it means 0.5 dB power attenuation (−0.5 dB), when the power control command is set to “011”, it means the current power maintenance (0 dB) of 0 dB, when the power control command is set to “10”, it means 0.5 dB power increase (+0.5 dB) and when the power control command is set to “11”, it means 1.0 dB power increase (+1.0 dB)

For the power control bits b=‘10’, indicating that the power control command is 3 bit. Wherein, when the power control command is set to ‘000’, it means 1.5 dB power attenuation (−1.5 dB), when the power control command is set to ‘111’, it means 2.0 dB power increase (+2.0 dB), and the power step size of the bitmap between ‘000’ and ‘111’ is set to 0.5 dB. That is, the power control command has the value between ‘000’ and ‘111’, and respectively indicating power change −1.5 dB (000), −1.0 dB (001), −0.5 dB (010), 0 dB (011), +0.5 dB (100), +1.0 dB (101), +1.5 dB (110), and +2.0 dB (111).

For the power control bits b=‘11’, indicating that the power control command is 4 bit. Wherein, when the power control command is set to ‘0000’, it means 3.5 dB power attenuation (−3.5 dB), when the power control command is set to ‘1111’, it means 4.0 dB power increase (+4.0 dB), and the difference of the power step size between ‘0000’ and ‘1111’ is set to 0.5 dB. That is, the power control command has the value between ‘0000’ and ‘1111’, and respectively indicating power change −3.5 dB (0000), −3.0 dB (0001), −2.5 dB (0010), −2.0 dB (0011), −1.5 dB (0100), −1.0 dB (0101), −0.5 dB (0110), 0 db (0111), +0.5 dB (1000), +1.0 dB (1001), +1.5 dB (1010), +2.0 dB (1011), +2.5 dB (1100), +3.0 dB (1101), +3.5 dB (1110), and +4.0 dB (1111).

The No. PC commands p indicates the number of bit included in the power control bitmap indicator. For example, the number of bit included in the power control bitmap indicator is “4*(p+1)”. Therefore, if the number of bit included in the power control bitmap is “20” the value of “p” has a binary number ‘0100(4)’ value.

The power control bitmap indicator indicates whether the power control command of each mobile station exists. And the size of the power control bitmap indicator is “4*(p+1)”. The i^(th) bit is associated with a mobile station allocated an i^(th) CQICH among the mobile stations allocated CQICHs, in the CQICH allocation information of a frame (for example, N^(th) frame) that goes ahead of the current frame (for example, (n+N)^(th) frame) by a frame offset (for example, n). If the i^(th) bit of the power control bitmap indicator is ‘0’, the power control bitmap has no power control command for the i^(th) mobile station. If, however, the i^(th) bit of the power control bitmap indicator is ‘1’, the power control bitmap has a power control command for the i^(th) mobile station. When the number of ‘1’s included in the power control bitmap indicator is I, the power control bitmap has I power control commands.

The power control bitmap includes the power control command and has the size of 4*(p+1)(b+1) bit. Each power control command has the size between 1 bit to 4 bit according to the value of b. And, the power control command is mapped with the power control information according to each bit value. Accordingly, the MS performs the power control using the power control information. For example, when the power control command is ‘1100’, the MS increases the current power by 2.5 dB. If the number of “1”s in the power control bitmap indicator is I, the power control bitmap includes one power control command. Each sequence of the power control command included in the power control bitmap is the same as each sequence of the MS having the bit value of “1” in the power control bitmap indicator.

The BS transmits the power control information element. The MS receiving the power control information element determines whether the MS's power control command exists according to the power control bitmap indicator, if the value of the power control command bits (b) is not “0” (b=00), that is, the MS determines that the power control bitmap indicator of the MS is ‘1’ or ‘0’. As a result, if the power control command exists (that is, the power control bitmap indicator of the MS is “1”), the MS obtains the power control information corresponding to the MS from the power control bitmap and performs the power control.

The power control information element shown in Table 8 includes at least the frame offset, the power control command bit number, the power control command number, the power control bitmap indicator, and the power control bitmap, and transmit them.

As the power command values corresponding to the frame offset, the No. PC command bits, No. PC commands, the power control bit, and the power control bit value respectively are shown as examples, the power command values are not limited by the values shown in Table 8, and the values can be changed, for example, based on the system situation, the user setup, etc.

As described in Table 8, the BS performs the following operation if the power command bits (b) is “00”.

The BS receives the CQI of each MS through already allocated CQICH in order to receive the CQI of the MS from the MS in the cell of the BS, and generates the power control information of each MS according to the received CQI. Herein, for example, the CQICH is used for generating the power control. Furthermore, for example, the power control information can be generated by using the uplink traffic bursts of the MS or the uplink traffic burst of the MS corresponding to the CQICH. Or the power control information can generate both the CQI received from the MS and the uplink traffic burst by considering them.

Next, the BS selects the power control command of the MS which will transmit the power control command. And, for the example, the BS maps, to the power control bitmap, the selected power control command according to the CQICH allocation information.

The BS additionally includes the additional information such as the power control bitmap indicator, etc, to the power control message and transmits to the MS. Herein, the power control message includes the power control bitmap. That is, the power control message includes at least one parameter among each parameter of the power control information element as described in Table 8.

Below is the operation of the MS receiving the power control message of the BS.

The MS detects the power control bitmap indicator and the power control bitmap from the received power control message. And the MS verifies the power control bitmap indicator according to the CQICH location of the MS in the CQICH of the frame corresponding to the frame offset. At this time, the MS verifies whether the power control command exists. If the power control command exists, the MS detects the power control command included in the power control bitmap, and controls the transmission power of the MS according to the detected power control command.

Further, for the example shown in FIG. 8, if the BS generates the power control information as described in the step 801 of FIG. 8, the BS can generates the power control information by using the uplink traffic burst of the MS corresponding to the CQICH as well as the CQICH, or the power control information by using only the uplink traffic burst.

For example, the connection ID (or the mobile station identification information) corresponding to the CQICH allocation information as described in Table 7 or 8 and the allocation sequence information can be substituted as the allocation information of the traffic burst. Accordingly, the power control information can be generated according to the allocation sequence of the traffic burst to the MS corresponding to the allocation information of the traffic burst.

For example, if the power control information of Table 7 is generated, the power control bitmap can be generated according to the allocation information of the traffic burst. Further, if the power control information of Table 8 is generated, the power control bitmap indicator can be generated according to the allocation information of the traffic burst. Further, in order to determining the increase/decrease of power of the MS, the CQICH together with the uplink traffic burst received from the MS can be used.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 

1. A method for controlling power at a base station in a communication system, the method comprising: transmitting, to at least one mobile station, first allocation information including connection identifiers of mobile stations; and transmitting power control information corresponding to the first allocation information to the mobile stations.
 2. The method of claim 1, wherein the power control information comprises at least one of a power control information bitmap indicator and a power control bitmap.
 3. The method of claim 2, wherein the power control information bitmap indicator comprises power control information bits indicating presence/absence of a power control command for each of the mobile stations.
 4. The method of claim 2, wherein the power control bitmap comprises power control commands allocated to the mobile stations.
 5. The method of claim 2, wherein the power control bitmap sequentially comprises power control commands for the mobile stations according to an order of bits included in the power control information bitmap indicator.
 6. The method of claim 1, wherein the power control information comprises at least one of a frame offset indicating location information of a particular frame including Channel Quality Information Channel (CQICH) allocation information corresponding to information indicated by the power control information bitmap indicator, and a number of bits included in the power control information bitmap indicator.
 7. A method for controlling power at a mobile station in a communication system, the method comprising: receiving first allocation information including a connection identifier of the mobile station; and detecting power control information corresponding to the first allocation information, and performing power control depending thereon.
 8. The method of claim 7, wherein the power control information comprises at least one of a power control information bitmap indicator and a power control bitmap.
 9. The method of claim 8, wherein the power control information bitmap indicator comprises power control information bits indicating presence/absence of a power control command for each of the mobile stations.
 10. The method of claim 8, wherein the power control bitmap comprises power control commands allocated to the mobile stations.
 11. The method of claim 8, wherein the power control bitmap sequentially comprises power control commands for the mobile stations according to an order of bits included in the power control information bitmap indicator.
 12. The method of claim 7, wherein the power control information comprises at least one of a frame offset indicating location information of a particular frame including Channel Quality Information Channel (CQICH) allocation information corresponding to information indicated by the power control information bitmap indicator, and a number of bits included in the power control information bitmap indicator.
 13. A system for controlling power in a communication system, the system comprising: a base station for transmitting, to at least one mobile station, first allocation information including connection identifiers of mobile stations, and transmitting power control information corresponding to the first allocation information to the mobile stations; and a mobile station for receiving the first allocation information, detecting power control information corresponding to the first allocation information, and performing power control depending thereon.
 14. The system of claim 13, wherein the power control information comprises at least one of a power control information bitmap indicator and a power control bitmap.
 15. The system of claim 14, wherein the power control information bitmap indicator comprises power control information bits indicating presence/absence of a power control command for each of the mobile stations.
 16. The system of claim 14, wherein the power control bitmap comprises power control commands allocated to the mobile stations.
 17. The system of claim 14, wherein the power control bitmap sequentially comprises power control commands for the mobile stations according to an order of bits included in the power control information bitmap indicator.
 18. The system of claim 13, wherein the power control information comprises at least one of a frame offset indicating location information of a particular frame including Channel Quality Information Channel (CQICH) allocation information corresponding to information indicated by the power control information bitmap indicator, and a number of bits included in the power control information bitmap indicator. 